Reinforced thermoplastic resin compositions in which glass fibers are blended are excellent in mechanical characteristics (such as impact strength and flexural properties) and moldability. Therefore, they can be substituted for metal materials used for manufacturing various components. Thus, it is possible to produce lighter components and reduce components count. Reinforced thermoplastic resin compositions blended with long glass fibers are known as molding materials providing moldings excellent particularly in mechanical strength because they suffer less damage of the fibers when molded (for example, refer to Patent Documents 1 and 2).
On the other hand, polyamide is a thermoplastic resin widely used in automobiles, machine-related materials, building materials, home equipment components, and the like. It is disclosed that a terminal group ratio of polyamide is defined for improving thermal stability and weatherability in a resin composition containing polyamide (for example, refer to Patent Documents 3, 4 and 5).
Automobile components are liable to be degraded due to heat. However, use of a resin composition excellent in thermal stability as a raw material will prolong product life of resultant components. As a thermal stabilizer used for this purpose, examples of a copper compound and an iodine compound are disclosed (for example, refer to Patent Documents 3, 4 and 5).
However, automobile underhood components (for example, engine head covers, oil pans, chain covers, oil filter brackets, crankshaft brackets, and the like), which are used at higher temperatures for a long period of time than other common automobile components and require close contact with other metal components and air tightness, are required to have impact resistance, dimensional stability and the like in addition to higher thermal stability. In this respect, conventional resin compositions have been unsatisfactory.    Patent Document 1: Japanese Patent Publication No. 63-37694    Patent Document 2: Japanese Patent Laid-Open No. 5-162124    Patent Document 3: Japanese Patent Laid-Open No. 6-32979    Patent Document 4: Japanese Patent Laid-Open No. 2003-55549    Patent Document 5: Japanese Patent Laid-Open No. 2002-179910